Loading...
1/*
2 * Copyright (C) 2005 Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
3 * Licensed under the GPL
4 */
5
6#include <linux/percpu.h>
7#include <linux/sched.h>
8#include <linux/syscalls.h>
9#include <linux/uaccess.h>
10#include <asm/ptrace-abi.h>
11#include <os.h>
12#include <skas.h>
13#include <sysdep/tls.h>
14#include <asm/desc.h>
15
16/*
17 * If needed we can detect when it's uninitialized.
18 *
19 * These are initialized in an initcall and unchanged thereafter.
20 */
21static int host_supports_tls = -1;
22int host_gdt_entry_tls_min;
23
24static int do_set_thread_area(struct user_desc *info)
25{
26 int ret;
27 u32 cpu;
28
29 cpu = get_cpu();
30 ret = os_set_thread_area(info, userspace_pid[cpu]);
31 put_cpu();
32
33 if (ret)
34 printk(KERN_ERR "PTRACE_SET_THREAD_AREA failed, err = %d, "
35 "index = %d\n", ret, info->entry_number);
36
37 return ret;
38}
39
40/*
41 * sys_get_thread_area: get a yet unused TLS descriptor index.
42 * XXX: Consider leaving one free slot for glibc usage at first place. This must
43 * be done here (and by changing GDT_ENTRY_TLS_* macros) and nowhere else.
44 *
45 * Also, this must be tested when compiling in SKAS mode with dynamic linking
46 * and running against NPTL.
47 */
48static int get_free_idx(struct task_struct* task)
49{
50 struct thread_struct *t = &task->thread;
51 int idx;
52
53 for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
54 if (!t->arch.tls_array[idx].present)
55 return idx + GDT_ENTRY_TLS_MIN;
56 return -ESRCH;
57}
58
59static inline void clear_user_desc(struct user_desc* info)
60{
61 /* Postcondition: LDT_empty(info) returns true. */
62 memset(info, 0, sizeof(*info));
63
64 /*
65 * Check the LDT_empty or the i386 sys_get_thread_area code - we obtain
66 * indeed an empty user_desc.
67 */
68 info->read_exec_only = 1;
69 info->seg_not_present = 1;
70}
71
72#define O_FORCE 1
73
74static int load_TLS(int flags, struct task_struct *to)
75{
76 int ret = 0;
77 int idx;
78
79 for (idx = GDT_ENTRY_TLS_MIN; idx < GDT_ENTRY_TLS_MAX; idx++) {
80 struct uml_tls_struct* curr =
81 &to->thread.arch.tls_array[idx - GDT_ENTRY_TLS_MIN];
82
83 /*
84 * Actually, now if it wasn't flushed it gets cleared and
85 * flushed to the host, which will clear it.
86 */
87 if (!curr->present) {
88 if (!curr->flushed) {
89 clear_user_desc(&curr->tls);
90 curr->tls.entry_number = idx;
91 } else {
92 WARN_ON(!LDT_empty(&curr->tls));
93 continue;
94 }
95 }
96
97 if (!(flags & O_FORCE) && curr->flushed)
98 continue;
99
100 ret = do_set_thread_area(&curr->tls);
101 if (ret)
102 goto out;
103
104 curr->flushed = 1;
105 }
106out:
107 return ret;
108}
109
110/*
111 * Verify if we need to do a flush for the new process, i.e. if there are any
112 * present desc's, only if they haven't been flushed.
113 */
114static inline int needs_TLS_update(struct task_struct *task)
115{
116 int i;
117 int ret = 0;
118
119 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
120 struct uml_tls_struct* curr =
121 &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
122
123 /*
124 * Can't test curr->present, we may need to clear a descriptor
125 * which had a value.
126 */
127 if (curr->flushed)
128 continue;
129 ret = 1;
130 break;
131 }
132 return ret;
133}
134
135/*
136 * On a newly forked process, the TLS descriptors haven't yet been flushed. So
137 * we mark them as such and the first switch_to will do the job.
138 */
139void clear_flushed_tls(struct task_struct *task)
140{
141 int i;
142
143 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
144 struct uml_tls_struct* curr =
145 &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
146
147 /*
148 * Still correct to do this, if it wasn't present on the host it
149 * will remain as flushed as it was.
150 */
151 if (!curr->present)
152 continue;
153
154 curr->flushed = 0;
155 }
156}
157
158/*
159 * In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a
160 * common host process. So this is needed in SKAS0 too.
161 *
162 * However, if each thread had a different host process (and this was discussed
163 * for SMP support) this won't be needed.
164 *
165 * And this will not need be used when (and if) we'll add support to the host
166 * SKAS patch.
167 */
168
169int arch_switch_tls(struct task_struct *to)
170{
171 if (!host_supports_tls)
172 return 0;
173
174 /*
175 * We have no need whatsoever to switch TLS for kernel threads; beyond
176 * that, that would also result in us calling os_set_thread_area with
177 * userspace_pid[cpu] == 0, which gives an error.
178 */
179 if (likely(to->mm))
180 return load_TLS(O_FORCE, to);
181
182 return 0;
183}
184
185static int set_tls_entry(struct task_struct* task, struct user_desc *info,
186 int idx, int flushed)
187{
188 struct thread_struct *t = &task->thread;
189
190 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
191 return -EINVAL;
192
193 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls = *info;
194 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present = 1;
195 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed = flushed;
196
197 return 0;
198}
199
200int arch_set_tls(struct task_struct *new, unsigned long tls)
201{
202 struct user_desc info;
203 int idx, ret = -EFAULT;
204
205 if (copy_from_user(&info, (void __user *) tls, sizeof(info)))
206 goto out;
207
208 ret = -EINVAL;
209 if (LDT_empty(&info))
210 goto out;
211
212 idx = info.entry_number;
213
214 ret = set_tls_entry(new, &info, idx, 0);
215out:
216 return ret;
217}
218
219static int get_tls_entry(struct task_struct *task, struct user_desc *info,
220 int idx)
221{
222 struct thread_struct *t = &task->thread;
223
224 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
225 return -EINVAL;
226
227 if (!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present)
228 goto clear;
229
230 *info = t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls;
231
232out:
233 /*
234 * Temporary debugging check, to make sure that things have been
235 * flushed. This could be triggered if load_TLS() failed.
236 */
237 if (unlikely(task == current &&
238 !t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed)) {
239 printk(KERN_ERR "get_tls_entry: task with pid %d got here "
240 "without flushed TLS.", current->pid);
241 }
242
243 return 0;
244clear:
245 /*
246 * When the TLS entry has not been set, the values read to user in the
247 * tls_array are 0 (because it's cleared at boot, see
248 * arch/i386/kernel/head.S:cpu_gdt_table). Emulate that.
249 */
250 clear_user_desc(info);
251 info->entry_number = idx;
252 goto out;
253}
254
255SYSCALL_DEFINE1(set_thread_area, struct user_desc __user *, user_desc)
256{
257 struct user_desc info;
258 int idx, ret;
259
260 if (!host_supports_tls)
261 return -ENOSYS;
262
263 if (copy_from_user(&info, user_desc, sizeof(info)))
264 return -EFAULT;
265
266 idx = info.entry_number;
267
268 if (idx == -1) {
269 idx = get_free_idx(current);
270 if (idx < 0)
271 return idx;
272 info.entry_number = idx;
273 /* Tell the user which slot we chose for him.*/
274 if (put_user(idx, &user_desc->entry_number))
275 return -EFAULT;
276 }
277
278 ret = do_set_thread_area(&info);
279 if (ret)
280 return ret;
281 return set_tls_entry(current, &info, idx, 1);
282}
283
284/*
285 * Perform set_thread_area on behalf of the traced child.
286 * Note: error handling is not done on the deferred load, and this differ from
287 * i386. However the only possible error are caused by bugs.
288 */
289int ptrace_set_thread_area(struct task_struct *child, int idx,
290 struct user_desc __user *user_desc)
291{
292 struct user_desc info;
293
294 if (!host_supports_tls)
295 return -EIO;
296
297 if (copy_from_user(&info, user_desc, sizeof(info)))
298 return -EFAULT;
299
300 return set_tls_entry(child, &info, idx, 0);
301}
302
303SYSCALL_DEFINE1(get_thread_area, struct user_desc __user *, user_desc)
304{
305 struct user_desc info;
306 int idx, ret;
307
308 if (!host_supports_tls)
309 return -ENOSYS;
310
311 if (get_user(idx, &user_desc->entry_number))
312 return -EFAULT;
313
314 ret = get_tls_entry(current, &info, idx);
315 if (ret < 0)
316 goto out;
317
318 if (copy_to_user(user_desc, &info, sizeof(info)))
319 ret = -EFAULT;
320
321out:
322 return ret;
323}
324
325/*
326 * Perform get_thread_area on behalf of the traced child.
327 */
328int ptrace_get_thread_area(struct task_struct *child, int idx,
329 struct user_desc __user *user_desc)
330{
331 struct user_desc info;
332 int ret;
333
334 if (!host_supports_tls)
335 return -EIO;
336
337 ret = get_tls_entry(child, &info, idx);
338 if (ret < 0)
339 goto out;
340
341 if (copy_to_user(user_desc, &info, sizeof(info)))
342 ret = -EFAULT;
343out:
344 return ret;
345}
346
347/*
348 * This code is really i386-only, but it detects and logs x86_64 GDT indexes
349 * if a 32-bit UML is running on a 64-bit host.
350 */
351static int __init __setup_host_supports_tls(void)
352{
353 check_host_supports_tls(&host_supports_tls, &host_gdt_entry_tls_min);
354 if (host_supports_tls) {
355 printk(KERN_INFO "Host TLS support detected\n");
356 printk(KERN_INFO "Detected host type: ");
357 switch (host_gdt_entry_tls_min) {
358 case GDT_ENTRY_TLS_MIN_I386:
359 printk(KERN_CONT "i386");
360 break;
361 case GDT_ENTRY_TLS_MIN_X86_64:
362 printk(KERN_CONT "x86_64");
363 break;
364 }
365 printk(KERN_CONT " (GDT indexes %d to %d)\n",
366 host_gdt_entry_tls_min,
367 host_gdt_entry_tls_min + GDT_ENTRY_TLS_ENTRIES);
368 } else
369 printk(KERN_ERR " Host TLS support NOT detected! "
370 "TLS support inside UML will not work\n");
371 return 0;
372}
373
374__initcall(__setup_host_supports_tls);
1/*
2 * Copyright (C) 2005 Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
3 * Licensed under the GPL
4 */
5
6#include <linux/percpu.h>
7#include <linux/sched.h>
8#include <linux/syscalls.h>
9#include <linux/uaccess.h>
10#include <asm/ptrace-abi.h>
11#include <os.h>
12#include <skas.h>
13#include <sysdep/tls.h>
14
15/*
16 * If needed we can detect when it's uninitialized.
17 *
18 * These are initialized in an initcall and unchanged thereafter.
19 */
20static int host_supports_tls = -1;
21int host_gdt_entry_tls_min;
22
23int do_set_thread_area(struct user_desc *info)
24{
25 int ret;
26 u32 cpu;
27
28 cpu = get_cpu();
29 ret = os_set_thread_area(info, userspace_pid[cpu]);
30 put_cpu();
31
32 if (ret)
33 printk(KERN_ERR "PTRACE_SET_THREAD_AREA failed, err = %d, "
34 "index = %d\n", ret, info->entry_number);
35
36 return ret;
37}
38
39int do_get_thread_area(struct user_desc *info)
40{
41 int ret;
42 u32 cpu;
43
44 cpu = get_cpu();
45 ret = os_get_thread_area(info, userspace_pid[cpu]);
46 put_cpu();
47
48 if (ret)
49 printk(KERN_ERR "PTRACE_GET_THREAD_AREA failed, err = %d, "
50 "index = %d\n", ret, info->entry_number);
51
52 return ret;
53}
54
55/*
56 * sys_get_thread_area: get a yet unused TLS descriptor index.
57 * XXX: Consider leaving one free slot for glibc usage at first place. This must
58 * be done here (and by changing GDT_ENTRY_TLS_* macros) and nowhere else.
59 *
60 * Also, this must be tested when compiling in SKAS mode with dynamic linking
61 * and running against NPTL.
62 */
63static int get_free_idx(struct task_struct* task)
64{
65 struct thread_struct *t = &task->thread;
66 int idx;
67
68 if (!t->arch.tls_array)
69 return GDT_ENTRY_TLS_MIN;
70
71 for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
72 if (!t->arch.tls_array[idx].present)
73 return idx + GDT_ENTRY_TLS_MIN;
74 return -ESRCH;
75}
76
77static inline void clear_user_desc(struct user_desc* info)
78{
79 /* Postcondition: LDT_empty(info) returns true. */
80 memset(info, 0, sizeof(*info));
81
82 /*
83 * Check the LDT_empty or the i386 sys_get_thread_area code - we obtain
84 * indeed an empty user_desc.
85 */
86 info->read_exec_only = 1;
87 info->seg_not_present = 1;
88}
89
90#define O_FORCE 1
91
92static int load_TLS(int flags, struct task_struct *to)
93{
94 int ret = 0;
95 int idx;
96
97 for (idx = GDT_ENTRY_TLS_MIN; idx < GDT_ENTRY_TLS_MAX; idx++) {
98 struct uml_tls_struct* curr =
99 &to->thread.arch.tls_array[idx - GDT_ENTRY_TLS_MIN];
100
101 /*
102 * Actually, now if it wasn't flushed it gets cleared and
103 * flushed to the host, which will clear it.
104 */
105 if (!curr->present) {
106 if (!curr->flushed) {
107 clear_user_desc(&curr->tls);
108 curr->tls.entry_number = idx;
109 } else {
110 WARN_ON(!LDT_empty(&curr->tls));
111 continue;
112 }
113 }
114
115 if (!(flags & O_FORCE) && curr->flushed)
116 continue;
117
118 ret = do_set_thread_area(&curr->tls);
119 if (ret)
120 goto out;
121
122 curr->flushed = 1;
123 }
124out:
125 return ret;
126}
127
128/*
129 * Verify if we need to do a flush for the new process, i.e. if there are any
130 * present desc's, only if they haven't been flushed.
131 */
132static inline int needs_TLS_update(struct task_struct *task)
133{
134 int i;
135 int ret = 0;
136
137 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
138 struct uml_tls_struct* curr =
139 &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
140
141 /*
142 * Can't test curr->present, we may need to clear a descriptor
143 * which had a value.
144 */
145 if (curr->flushed)
146 continue;
147 ret = 1;
148 break;
149 }
150 return ret;
151}
152
153/*
154 * On a newly forked process, the TLS descriptors haven't yet been flushed. So
155 * we mark them as such and the first switch_to will do the job.
156 */
157void clear_flushed_tls(struct task_struct *task)
158{
159 int i;
160
161 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
162 struct uml_tls_struct* curr =
163 &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
164
165 /*
166 * Still correct to do this, if it wasn't present on the host it
167 * will remain as flushed as it was.
168 */
169 if (!curr->present)
170 continue;
171
172 curr->flushed = 0;
173 }
174}
175
176/*
177 * In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a
178 * common host process. So this is needed in SKAS0 too.
179 *
180 * However, if each thread had a different host process (and this was discussed
181 * for SMP support) this won't be needed.
182 *
183 * And this will not need be used when (and if) we'll add support to the host
184 * SKAS patch.
185 */
186
187int arch_switch_tls(struct task_struct *to)
188{
189 if (!host_supports_tls)
190 return 0;
191
192 /*
193 * We have no need whatsoever to switch TLS for kernel threads; beyond
194 * that, that would also result in us calling os_set_thread_area with
195 * userspace_pid[cpu] == 0, which gives an error.
196 */
197 if (likely(to->mm))
198 return load_TLS(O_FORCE, to);
199
200 return 0;
201}
202
203static int set_tls_entry(struct task_struct* task, struct user_desc *info,
204 int idx, int flushed)
205{
206 struct thread_struct *t = &task->thread;
207
208 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
209 return -EINVAL;
210
211 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls = *info;
212 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present = 1;
213 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed = flushed;
214
215 return 0;
216}
217
218int arch_copy_tls(struct task_struct *new)
219{
220 struct user_desc info;
221 int idx, ret = -EFAULT;
222
223 if (copy_from_user(&info,
224 (void __user *) UPT_SI(&new->thread.regs.regs),
225 sizeof(info)))
226 goto out;
227
228 ret = -EINVAL;
229 if (LDT_empty(&info))
230 goto out;
231
232 idx = info.entry_number;
233
234 ret = set_tls_entry(new, &info, idx, 0);
235out:
236 return ret;
237}
238
239/* XXX: use do_get_thread_area to read the host value? I'm not at all sure! */
240static int get_tls_entry(struct task_struct *task, struct user_desc *info,
241 int idx)
242{
243 struct thread_struct *t = &task->thread;
244
245 if (!t->arch.tls_array)
246 goto clear;
247
248 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
249 return -EINVAL;
250
251 if (!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present)
252 goto clear;
253
254 *info = t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls;
255
256out:
257 /*
258 * Temporary debugging check, to make sure that things have been
259 * flushed. This could be triggered if load_TLS() failed.
260 */
261 if (unlikely(task == current &&
262 !t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed)) {
263 printk(KERN_ERR "get_tls_entry: task with pid %d got here "
264 "without flushed TLS.", current->pid);
265 }
266
267 return 0;
268clear:
269 /*
270 * When the TLS entry has not been set, the values read to user in the
271 * tls_array are 0 (because it's cleared at boot, see
272 * arch/i386/kernel/head.S:cpu_gdt_table). Emulate that.
273 */
274 clear_user_desc(info);
275 info->entry_number = idx;
276 goto out;
277}
278
279SYSCALL_DEFINE1(set_thread_area, struct user_desc __user *, user_desc)
280{
281 struct user_desc info;
282 int idx, ret;
283
284 if (!host_supports_tls)
285 return -ENOSYS;
286
287 if (copy_from_user(&info, user_desc, sizeof(info)))
288 return -EFAULT;
289
290 idx = info.entry_number;
291
292 if (idx == -1) {
293 idx = get_free_idx(current);
294 if (idx < 0)
295 return idx;
296 info.entry_number = idx;
297 /* Tell the user which slot we chose for him.*/
298 if (put_user(idx, &user_desc->entry_number))
299 return -EFAULT;
300 }
301
302 ret = do_set_thread_area(&info);
303 if (ret)
304 return ret;
305 return set_tls_entry(current, &info, idx, 1);
306}
307
308/*
309 * Perform set_thread_area on behalf of the traced child.
310 * Note: error handling is not done on the deferred load, and this differ from
311 * i386. However the only possible error are caused by bugs.
312 */
313int ptrace_set_thread_area(struct task_struct *child, int idx,
314 struct user_desc __user *user_desc)
315{
316 struct user_desc info;
317
318 if (!host_supports_tls)
319 return -EIO;
320
321 if (copy_from_user(&info, user_desc, sizeof(info)))
322 return -EFAULT;
323
324 return set_tls_entry(child, &info, idx, 0);
325}
326
327SYSCALL_DEFINE1(get_thread_area, struct user_desc __user *, user_desc)
328{
329 struct user_desc info;
330 int idx, ret;
331
332 if (!host_supports_tls)
333 return -ENOSYS;
334
335 if (get_user(idx, &user_desc->entry_number))
336 return -EFAULT;
337
338 ret = get_tls_entry(current, &info, idx);
339 if (ret < 0)
340 goto out;
341
342 if (copy_to_user(user_desc, &info, sizeof(info)))
343 ret = -EFAULT;
344
345out:
346 return ret;
347}
348
349/*
350 * Perform get_thread_area on behalf of the traced child.
351 */
352int ptrace_get_thread_area(struct task_struct *child, int idx,
353 struct user_desc __user *user_desc)
354{
355 struct user_desc info;
356 int ret;
357
358 if (!host_supports_tls)
359 return -EIO;
360
361 ret = get_tls_entry(child, &info, idx);
362 if (ret < 0)
363 goto out;
364
365 if (copy_to_user(user_desc, &info, sizeof(info)))
366 ret = -EFAULT;
367out:
368 return ret;
369}
370
371/*
372 * This code is really i386-only, but it detects and logs x86_64 GDT indexes
373 * if a 32-bit UML is running on a 64-bit host.
374 */
375static int __init __setup_host_supports_tls(void)
376{
377 check_host_supports_tls(&host_supports_tls, &host_gdt_entry_tls_min);
378 if (host_supports_tls) {
379 printk(KERN_INFO "Host TLS support detected\n");
380 printk(KERN_INFO "Detected host type: ");
381 switch (host_gdt_entry_tls_min) {
382 case GDT_ENTRY_TLS_MIN_I386:
383 printk(KERN_CONT "i386");
384 break;
385 case GDT_ENTRY_TLS_MIN_X86_64:
386 printk(KERN_CONT "x86_64");
387 break;
388 }
389 printk(KERN_CONT " (GDT indexes %d to %d)\n",
390 host_gdt_entry_tls_min,
391 host_gdt_entry_tls_min + GDT_ENTRY_TLS_ENTRIES);
392 } else
393 printk(KERN_ERR " Host TLS support NOT detected! "
394 "TLS support inside UML will not work\n");
395 return 0;
396}
397
398__initcall(__setup_host_supports_tls);